Members of the NZDF responded to the scene, at Okoromai Bay, on the Whangaparāoa Peninsula, in Auckland early this evening.
“After establishing a cordon around the beach at Okoromai Bay to prevent public access, the NZDF Explosive Ordnance Disposal team destroyed the item via a controlled demolition,” a spokeswoman said.
“Once the item was deemed safe, the cordon was lifted.”
Local resident Lee Durham, whose home overlooks the bay, said they were preparing dinner shortly before 6pm when an explosion went off.
“It shook our house and we were in a bit of a shock. We looked out and there was a big cloud of smoke going up.
“I immediately called Fire and Emergency. I drove down to see if I could offer any help, but there was Police and Army [personnel] there.”
He said it appeared that it was a controlled detonation, so knew it was all okay, he said.
The NZDF encouraged anyone who finds similar items to contact the Police or Coast Guard immediately to ensure they can be disposed of safely.
Sign up to The Daily H, a free newsletter curated by our editors and delivered straight to your inbox every weekday.